Hitherto, in conjunction with objects, especially food items, in view of nondestructive inspection in accordance with the optical characteristics of objects, there have been developed inspection methods that use near-infrared region wavelengths to thereby be capable of inspecting many inspection targets in a short time so as to be usable in, for example, food quality control.
As a method of this type, a method as disclosed in Japanese Patent Application Laid-open No. 2002-122538 is known. According to the method, a near-infrared wavelength of a 700 nm-1100 nm is irradiated externally on a liquid sample in a test tube; scattered reflected light, scattered transmitted light, or transmissive reflected light from the liquid sample is detected by an optical sensor to thereby measure near-infrared absorbance spectra of the liquid sample; and respective measurement values are substituted for a calibration line preliminarily created from spectra measured in a similar method. Thereby, the method measures the contents of components, such as lipid, protein, starch (sugar), iodine value and acid value, of the liquid sample.